The present invention is directed to power transmissions, and in particular to an electromechanical transmission useful for adding or removing power to or from a shaft or a wheel.
Automotive differentials allow two wheels mounted on output half shafts to rotate at different speeds, helping trucks and cars to remain stable in turns. However, in a conventional differential, when one wheel loses traction, the other wheel may also lose power. In a limited slip differential, when one wheel has less traction with the road than the other wheel, power is transferred from the slipping wheel to the non-slipping wheel. Under these conditions, the wheel that slips has an opportunity to recover traction, while the wheel that grips receives increased power to keep moving and perhaps to keep the vehicle moving.
Some positive limited-slip differentials are presently in the marketplace. One problem with such differentials is that they tend to be controlled by the relative speed of the wheels as well as a force or a preload applied to side gears in the differential. Another problem is that while power may be applied equally, it may be a very little amount of power to each wheel. At the same time, it seems clear that much more power is available, but is not being used. It would be useful if there were a way to allocate power among the half-shafts or axles of a vehicle, in such a way that the slipping wheel receives only the small amount of power it can use while the gripping wheel receives a greater share of power to keep the vehicle moving.
What is needed is a power or torque-allocating mechanism that would allow only a small amount of power to a slipping wheel and re-allocate power to keep the vehicle moving. What is needed is an improved power transmitter that will shift and transmit power reliably, while taking advantage of all the power that is available at a gearbox or differential. What is also needed is an improved method of allocating power between slipping and gripping wheels of an automobile or a truck.
One aspect of the invention is a torque controller to control output power to at least two shafts. The torque controller comprises a differential having at least a first and a second shaft, each shaft having an interface to a transfer assembly. The torque controller further comprises at least a first and a second transfer assembly, the transfer assemblies connected to each interface and to the differential. The torque controller also comprises a torque difference source connected to each transfer assembly, wherein the first output shaft and transfer assembly receive work from the differential, and the second transfer assembly and output shaft receive work from at least the torque difference source.
Another aspect of the invention is a method of transferring power from a first shaft output in a differential to a second shaft output. The method comprises providing power to a differential, and sensing a difference in shaft output power application. The method then determines whether a correction in output power is needed. If a correction is needed, the method then routes power from a first shaft of the differential to a torque difference source, and routes power from the torque difference source to a second shaft output of the differential. The method then includes continuing to sense and monitor shaft outputs of the differential.
Another aspect of the invention is a torque controller to control output power to at least two shafts. The torque controller comprises a differential having at least a first and a second output shaft, the first output shaft having an interface to a first transfer assembly and the second output shaft having an interface to a second transfer assembly. The torque controller includes a torque difference source connected to the first and second transfer assemblies. The torque controller also includes means for controlling power applied by the first shaft and transfer assembly to the torque difference source and for controlling power applied by the torque difference source to the second transfer assembly and shaft.
These and many other aspects and advantages of the invention will be seen in the figures and preferred embodiments of the invention described herein.